While solid state light sources, e.g., light emitting diodes (LEDs) may generate less thermal energy compared to traditional bulbs (e.g., incandescent light bulbs), solid state light sources nevertheless generate thermal energy which should be managed in order to control the junction temperature. A higher junction temperature generally correlates to lower light output, lower luminaire efficiency, and/or reduced life expectancy.
Solid-state illumination systems include heat sinks to dissipate thermal energy away from the solid state light source in order to manage the junction temperature. A two-component heat sink is known in US Pat. Pub. 2014/0338878 (Tessnow). Other examples of heat sinks and air flow are in U.S. Pat. No. 7,683,395 (Huber); U.S. Pat. No. 9,115,861 (Sieme); U.S. Pat. No. 6,497,507 (Weber); U.S. Pat. No. 7,329,033 (Glovatsky); Pub. US2011/0310631 (Davis); and European EP 2 020 569 (Barthel); and German DE 10 2011 084 114 (Wais).
It is known that solid-state light-emitting diodes (LEDs) are efficient and used in automotive low beam and high beam headlamps. Higher power LEDs are now used in such applications, such as those sold by OSRAM Opto Semiconductors under the trade designation Oslon Black Flat S (Model KW HLL531.TE) which has 5 chips generating 2000 lumens and a 20 Watt thermal load (28 total electrical Watts, 8 Watts emitted as light). Such LEDs need relatively large heat sinks. Since it is desired that the headlamps are moveable so as to be aimed, the heat sinks are internal to a sealed housing. The heat sinks for such large thermal loads are large and heavy, consuming about 500 grams of aluminum, which presents a lampset packaging problem. Simultaneously, however, the thermal power of these LEDs is nonetheless too small to melt ice or defog lenses as was commonly done by the traditional but less efficient filament incandescent or halogen lamps. Even when using the higher power LEDs and passive heat sinks the radiated heat remains behind the headlamp housing's bezel which conceals the light source and the front lens cover stays relatively cool. Conventional solutions have involved hot air generating fans with complicated air ducts that required breaking holes into the bezel, undesirable from a standpoint of a vehicle manufacturer's styling goals.